Enzyme deficiency: The body produces specific enzymes for dairy, protein, fats, and carbohydrates. If you don’t make enough of one (dairy-enzyme insufficiency is common)—or if you don’t have enough stomach acid to activate them—you’ll experience gas, bloating, and diarrhea when you eat that food.

Food intolerance or sensitivity. People who are sensitive to gluten, dairy, eggs, nuts, seafood, or other foods may have abdominal cramping and diarrhea after consuming those triggers. Symptoms may also be subtler, and include fatigue, itching, brain fog, dark circles under the eyes, migraines, or nasal congestion.

Gastroesophageal reflux disease. GERD is diagnosed when you have frequent and chronic heartburn or reflux—when acid and other stomach contents splash back into the esophagus and create a burning sensation in the abdomen, chest, or throat.

Irritable bowel syndrome. IBS is often diagnosed when docs can’t find any other reason for chronic bouts of abdominal pain, bloating, diarrhea, or constipation.

Leaky gut syndrome. You get frequent diarrhea, and you also seem to get more than your share of colds, low-grade fevers, body aches, chronic fatigue, and other infections. When you do get sick, it takes you longer than most to heal. You may also have anemia and other nutrient deficiencies.

Gut-supportive supplements

Aloe vera gel. It’s rich in mucopolysaccharides, effective anti-inflammatory agents that are treat GERD, gastritis, leaky gut, and other conditions. Dose: 2–3 ounces daily of a product containing standardized mucopolysaccharide amounts.

DGL. Deglycyrrhizinated licorice soothes the esophagus and stomach and acts as an antacid. Helps with GERD. Look for chocolate flavors, to make chewing more pleasant. Dose: 2–4 380-mg tablets, before meals.

Digestive enzymes. Helpful for gas, bloating, and lactose intolerance; check labels for enzymes that work at a range of pH levels, “so they can get the job done irrespective of gastric-acid production,” Vrablic says. For general support, choose a product with several types that help digest proteins, fats, carbohydrates, and fiber. For food sensitivities, try targeted products with lactase (for dairy) and specific proteases (for gluten and casein). A few enzymes can be animal-derived, but you can generally find vegetarian ones, too; check labels. Dose: One capsule, taken at the start of a meal.

Glutamine. This amino acid helps repair damaged intestinal cells, helpful for leaky gut. Dose: 1,000–3,000 mg three times daily. Back off to a lower dose if you start to get constipated.

Probiotics. Probiotic supplements restore beneficial bacteria lost after bouts of diarrhea, antibiotic use, or poor diet. They’re helpful for lactose intolerance, IBS, leaky gut—and balancing the immune system. Lipski often recommends Lactobacillus acidophilus and Bifidobacteria bifidum strains; in animal studies,B. bifidum improves mucosal barrier function and decreases inflammation, helpful for leaky gut. Dose: 1 billion–25 billion live organisms daily.